You live on a windy ridge. Sunshine is unreliable (imagine the west coast of the South Island), and you're a long way from the nearest power pole. The simple solution to your energy requirements is a micro wind generator, isn't it? The answer is "well, maybe." There are a surprising number of factors to consider before taking this route, not the least of which is cost, but in certain cases, wind generators can indeed have a significant role in either keeping you completely off the grid or complementing a normal electricity supply.
The first factor to consider is whether your site is really as windy as you think it is. Wind turbines need a surprising wind velocity (over 4.5mps or 16kph, although higher than this is better) to keep them operating efficiently, and of course, even if it blows a gale for a couple of months a year, you need to think carefully about, and preferably measure, what your wind supply is like during the calmer months of the year. Otherwise, you may find yourself with a costly system that only provides electricity once a week, or in June and July only, and you remain dependent on other power sources for most of the year. There are a variety of ways in which you can assess the level of wind capacity available to you, and some are detailed in a very comprehensive document from EECA, which also deals with small-scale solar and hydro schemes in addition to wind power. You can also find a great deal of useful information on domestic wind power on the New Zealand Wind Energy Association site.
The next item to consider is the cost, which is considerable. Most households will need a generation system of under 5kW, but this may cost anywhere from $20,000 to $100,000 or more installed, depending on whether you are intending to be linked to the grid or not. The cost of the turbine may only be 20-40% of the total installation cost, once inverters, turbine stands, transport, labour, and other expenses are included. It is more expensive to establish an off-grid system, as you must also invest in battery storage systems, and usually a backup generating system for emergencies or periods of low wind. This may involve diesel generators, photovoltaic systems, or micro-hydro, depending on your location and resources. Generally, wind generation can pay off if you are in a reliably windy area and are also a long way from the main electricity network: it can cost up to $25,000 per km to bring in an electricity line from the nearest available point.
As just mentioned, the actual turbine is only part of the story: you also need the infrastructure to support it (literally, in this case). A turbine has to have a very firm anchor, as it is subjected to considerable force during its working life. The turbine is generally mounted on a pole or tower, and in order to catch the most wind, the higher the tower the better. These supports are usually made of steel and can be either supported by guy-ropes, or self-supporting. The latter is less demanding on space, and has a better aesthetic appeal, but is generally more expensive. You need to remember that in order to carry out routine and essential maintenance, it is important to be able to get at, and in many cases lower the turbine – this may determine the type of support tower you use.
There are many different styles of both turbines and supports available, and it is important to assemble plenty of information before making a decision. What works in one location may not be the best for another. The basics can be found at the EECA and NZWEA sites mentioned earlier, and information from individual suppliers can also be helpful. You can find specific details on turbines at this site and here. For an unusual design, manufactured in New Zealand and using just a single blade and therefore claimed to be quieter than other designs, have a look here.
It is also important to remember that in installing a wind turbine system there are significant safety issues – the combination of rapidly rotating large blades, an electricity supply, and heights should not be taken lightly.
A final consideration is not to expect too much of your wind turbine. Generally, a micro or mini wind turbine will generate only 10-30% of its rated power output over a year, purely because wind speeds vary and effectiveness is very site-dependent. Taking the time to consult with an expert about siting may be very worthwhile, as the amount of energy available from the wind increases as the cube of the change in wind speed – so if the wind speed doubles, the power available is eight times as much. Keeping your turbine an appropriate distance from obstructions that cause turbulence or interfere with wind flow is also vital, but you may have to compromise in order to also minimise electrical losses and cabling costs – it is recommended that you should have the turbine within 100m of where the power will be used.
Although this may all sound daunting, there are many satisfied users of wind turbines in the more remote areas of New Zealand. Hunt around, talk to people who already have a system, learn as much as you can before making a decision, and you may be able to install a system that not only powers your house but allows you to sell back some surplus generation to the grid, depending on your location.
